Works with all K-mount lenses...unless you want AF or aperture control, let alone Pentax ergonomics or RAW quality. Sure most of the FF-capable lenses have aperture rings but honestly, why bother with MF and stop-down metering every time you want to slap an FA ltd on there?

I prefer shooting manual focus lenses on the A7/R than I do any SLR body. They are easier to focus and metering is perfect.

The only thing you really lose in this case is AF.

Using the A7R I get full TTL flash support with any lens ever, plus TTL is very accurate when your imaging sensor is your light meter.

Eric

Gee. I have ordered a K NEX adapter.

And I have a much coveted AF280T Pentax flash (TTL) and a whole pile of Pentax prime lenses. I do BIF with manual lenses so manual focus is just right on for me .